1,720,986 research outputs found
Optimization criteria of TMD to reduce vibrations generated by the wind in a slender structure
No full textThis paper deals with the reduction of vibrations caused by wind load in slender structures. The structure is modeled as a Single-Degree-of-Freedom system and the wind load is estimated through the pre-filter technique: the aerodynamic force is a function of White Noise filtered by a simple oscillator. Two optimization criteria to calculate the best values of the frequency and the damping ratio of the Tuned Mass Damper (TMD) are compared here. The aim of the first criterion is the reduction of the displacement of the top end of the structure, while the aim of the second criterion is the reduction of the inertial acceleration of the top end of the structure. The comparison of the two criteria is carried out through sensitivity analyses for different environmental conditions and system configurations. The comparison shows that the acceleration criterion is more attractive only for some conditions. Moreover, it is plain that the different efficiencies of the TMD optimized through each of two criteria are related to the mass ratio. Finally, the optimization criteria are applied to estimate the TMD design parameters to reduce the vibrations due to wind load in a lighting tower
Optimum design of tuned mass dampers for different earthquake ground motion parameters and models
No full textTuned mass dampers are frequently used for passive control of vibrations in civil structures subject to seismic and wind actions. Their efficiency depends on selection of their mechanical properties in relation to main system and excitation characteristics. This paper proposes an optimum design strategy of single tuned mass dampers to control vibrations of principal mode of structures excited by earthquake ground motion. The main purpose of the paper is to investigate the influence of the time modulation of earthquake excitation upon the optimal tuned mass dampers design parameters: frequency and damping ratio. The study is based on numerical analyses carried out with different stochastic models for earthquakes: a simple filtered white noise model and two time modulated filtered white noise models. The numerical analyses are carried out to solve an optimization problem with a performance index defined by the reduction of the standard deviation of either the structure displacement or its inertial acceleration as objective function. To complete the work, the influence of the bandwidth excitation over the values of the optimal tuned mass damper parameters is investigated, as well the optimum mass ratio and the structure frequency. The results of the numeral analyses carried out infer that the earthquake excitation characteristics, including its modulation in time domain, highly affect the optimum tuned mass damper design parameters values
Modelling of stochastic process for earthquake representation as alternative way for structural seismic analysis: past, present and future
No full textModelling of stochastic process for earthquake representation as alternative way for structural seismic analysis: past, present and future
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Optimization criteria for the TDM design in slender structures excited by wind load
No full textThe Tuned Mass Damper (TMD) is the simplest of the passive control devices used in many slender structures to protect them from damages and failure produced by dynamic loads. A single TMD is used to control vibrations in a real structure when a single vibrational mode involves the greatest part of the modal mass. This paper deals with the reduction of vibrations in slender structures due to the wind load. The structure is modelled as a Single Degree of Freedom (SDoF) system and the wind load is estimated through the pre-filter technique: the aerodynamic force is a function of a filtered White Noise. Several optimization criteria have been proposed to estimate the optimum TMD design parameters that provide the best performance in the structural vibration reduction. Two different criteria to optimize the frequency and the damping ratio of the TMD are here proposed. The reduction of the displacement and the acceleration of the structure at its top are the aims respectively of the first and the second optimization criteria proposed. A comparison of the design parameters and the performance obtain from the application of the two criteria is presented. Moreover, sensitivity analyses for different environment conditions and system configuration are carried out. The comparison of the two optimization criteria and the sensitivity analyses show that the acceleration criterion is more attractive. Finally, the two optimization criteria are applied to estimate the TMD design parameters to reduce the vibrations due to the wind load in a lighting towe
Optimization of tuned mass dampers subject to non-stationary random excitation
No full textThis paper presents a stochastic approach for the optimum design of a single tuned mass damper (TMD) protecting a linear mechanical system. The optimum strategy is directed towards maximizing the effectiveness of the TMD in reducing the vibration level in the system to be protected. This performance is evaluated on the basis of the reduction of the root-mean-square displacement and acceleration of the main system. Several numerical analyses are carried out for assessing the influence of the system and the excitation characteristics of the optimum TMD. In particular, a comparison between the TMD optimum designs for a system excited by stationary and nonstationary filtered white noise is presented. Finally, the advantages of modelling the seismic excitation as non-stationary filtered white noise for the optimum TMD design are clearly stated
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